As widespread use of portable electronic products such as high quality smartphones, Pads and the like, requirements on earphones capable of cooperating with the electronic products are increasingly higher; the earphones are required to have a small size and hi-fi sound quality performances capable of realistically representing various sound effects, and thus hi-fi earphones become the market trend. Earphones are divided into in-ear, on-ear and semi in-ear earphones based on wearing styles. As the in-ear earphones having poorer wearing comfortableness, and causing potential security risks due to insufficient perception to background sounds when used, as well as considerations of hearing protection, the on-ear and semi in-ear earphones are increasingly preferred by consumers.
Due to sound leakage naturally occurred between the earphone and ear canal when the earphone is worn, the low-frequency performance of the on-ear/semi in-ear earphones is usually insufficient. It is a frequently-used solution that the size of an extension tube for accommodating the audio signal wire is enlarged, and openings for communicating with outside are provided at earphone stem, such that the extension tube of the audio signal wire becomes a acoustic guide channel capable of enhancing low-frequency effects simultaneously; or a acoustic guide channel structure for connecting the rear acoustic cavity with outside is added in the same direction as the extension tube of the audio signal wire. Such structures of acoustic guide channels for enhancing low-frequency effect will increase the size of the earphone, and affect appearance thereof. Moreover, the audio signal wire is fixed in the rear acoustic cavity through wire-knot generally, thus the wire knots will block the acoustic guide channels to varying degrees, and affect the effect of the acoustic guide channels with the above structures.
Furthermore, as on-ear and semi in-ear earphone usually utilize a loudspeaker unit with a diameter more than 13 mm, the volume of the rear acoustic cavity of the earphone is usually relatively larger based on the requirement of appearance design, such that the middle-frequency performance of the earphone is not satisfactory. The volume of the rear acoustic cavity is diminished by adding injection parts in the rear acoustic cavity, such that the cost is relatively higher.
Consequently, it is necessary to improve the earphones with the above structures to overcome the drawbacks in the design technique for the existing earphones.